The present invention relates to a golf ball capable of enhancing the durability to increase the carry of the ball with less variation in carry of the ball.
Golf balls have been required to be improved in terms of player""s soft feeling of hitting and carrying performance; however, it has been regarded as difficult to make these properties compatible with each other for the following reasons:
(1) If a solid core is softened for ensuring the player""s soft feeling, a deformed amount of the hit ball becomes large, to degrade the durability against cracking.
(2) If both the solid core and a cover are softened for ensuring both the player""s soft feeling and durability against cracking, the resilience and initial velocity of the ball are reduced, to sacrifice the carrying performance.
(3) Depending on a difference between the geometric position of the center of gravity of each golf ball and the actual position of the center of gravity of the ball, which difference is possibly caused at the time of production of the ball, there occur large variations in carry among the golf balls.
To solve the above problems, Japanese Patent Laid-open No. 2000-5341 has proposed an excellent golf ball characterized by combining a solid core, which is softened to improve player""s soft feeling and durability against cracking, with a cover to which a reinforcement filler is added.
For such a golf ball, it has been also required to increase the carry of the ball while keeping high durability, and to suppress variations in carry among golf balls of the same kind.
An object of the present invention is to provide a golf ball capable of enhancing the durability to increase the carry of the ball with less variations in carry of the ball.
To achieve the above object, the present inventor has earnestly examined and found that at the time of hitting a golf ball, the center of gravity of the ball is shift by deformation of the ball caused by hitting the ball, and that with respect to the relationship between the solid core and the cover of the golf ball disclosed in Japanese Patent Laid-open No. 2000-5341, if the specific gravity of the cover is larger than the specific gravity of the solid core, the shift of the center of gravity of the ball due to deformation of the ball caused until the initial stage of flying since immediately after hitting is liable to become large, and particularly, if the solid core becomes softer, since the shift of the center of gravity of the ball becomes larger, the carrying performance may be degraded.
To cope with such an inconvenience, the present inventor has further examined, and eventually found that a golf ball including a solid core and a cover of at least one layer; wherein each of a specific gravity of the solid core and a specific gravity of the cover is nearly equal to a value (S) of a relation expression given by S=W/[(xcfx80/6)xc3x97D3], where W is a weight of the golf ball and D is a diameter of the golf ball, is advantageous in that since the specific gravity of the entire ball is equalized, the spin performance is stabilized, and the continuation of flying of the ball becomes very high without runout of the ball, it is possible to enhance the carrying performance, reduce the possibility of drop of the ball, improve the durability, reduce variations in carry among golf balls of the same kind, and increase the carry of the ball. The present invention has been accomplished on the basis of the above knowledge.
According to the present invention, there is provided a golf ball including a solid core and a cover of at least one layer; wherein each of a specific gravity of the solid core and a specific gravity of the cover is nearly equal to a value (S) of a relation expression given by S=W/[(xcfx80/6)xc3x97D3], where W is a weight of the golf ball and D is a diameter of the golf ball.
A surface hardness of the solid core is preferably higher than a center hardness of the solid core by 8 to 20 in JIS-C hardness.
A surface hardness of the golf ball is preferably higher than a center hardness of the solid core by 20 to 45 in JIS-C hardness.
A surface hardness of the golf ball is preferably higher than a surface hardness of the solid core by 10 to 30 in JIS-C hardness.
A flexural amount of the golf ball, measured by applying a load of 98 to 1274N thereto, is preferably in a range of 3.5 to 6.0 mm.
A diameter (D) of the golf ball is preferably in a range of 42.60 to 42.78 mm.
A weight (W) of the golf ball is preferably in a range of 45.1 to 45.9 g.
The golf ball is preferably a two-piece solid golf ball including a solid core and a cover of one layer.
A ratio of a specific gravity of the solid core to a specific gravity of the cover (specific gravity of solid core/specific gravity of cover) is preferably in a range of 0.910 to 1.095.